The present invention relates to construction and building materials and methods and more particularly, to adjustable height concrete expansion joints enabling easy height adjustment for accurate leveling of concrete surfaces, and providing pre-fabricated joints for same.
Concrete expansion joints are an essential component in the proper construction of many large concrete surfaces, such as floors, roofs, parking lots, roads, airport runways and the like. These joints enable expansion and contraction of the concrete or mortar surfaces based on surrounding temperatures, which reach hot and cold extremes, respectively, in summer and winter periods, and other factors including shifting of soil underneath the slabs. These joints are meant to eliminate the deterioration of the slab due to random cracks which otherwise form in the concrete.
As used herein the term xe2x80x9cjointsxe2x80x9d applies equally to expansion and contraction joints.
In pouring concrete over a large surface and insuring that it spreads evenly, reference marks are needed to indicate the height of the concrete slab. In many cases where forms are used to define areas into which concrete is poured, flexible joint materials are placed into the grooves resulting when the forms are removed. A leveling string is stretched from a stud at the corners of the forms, and the stud is vertically adjustable by use of a nut, to provide the reference for pouring the concrete. This task requires much time and effort and still leaves irregularities in the concrete surface.
Existing methods of providing joints in concrete slabs include the method of saw cutting a groove for the joint in the solid concrete, and this requires specially designed diamond saw cutting blades, which have a very short useful life and are very expensive. In addition, there is a limiting time factor, since the sawcut must be performed within a short period after pouring the concrete.
In U.S. Pat. No. 4,050,206 to Utsuyama, an improved jointing material is disclosed for placement on a support assembly having an adjustable height to provide a reference surface. The support assembly comprises leg assemblies which are adjusted to the desired reference surface height, by bending the legs toward and away from each other. This adjustment is neither consistent nor convenient for all of the support assemblies.
A product commercially available from Thorbjorn Lund Sweden, known as Combiform, discloses a method of supporting a screed rail with a ground plate having adjustment screws to adjust the rail height. The adjusting screws are supported by a ground plate placed under the rail, so that these screws are at a low level, and once concrete is poured over these, no further adjustment is possible. This limits flexibility in construction.
U.S. Pat. No. 4,198,176 to Bentz discloses a concrete expansion joint forming structure in which a U-shaped metallic sheet holder supports an expansion joint. The holder is supported on a pair of chisel-shaped pegs driven into the ground before pouring concrete around the area to set the expansion joints. No height adjustment is described for the pegs once they are set.
U.S. Pat. No. 4,875,801 to Montrym discloses an expansion joint brace with ground pegs for setting the brace before pouring concrete. As before, no height adjustment is described for the pegs once they are set.
In U.S. Pat. No. 4,979,846 to Hill et al., there is disclosed a contraction joint for concrete linings in which a triangular-shaped section is placed with its apex protruding over a reference surface of concrete, but without a height adjustment.
Therefore, it would be desirable to provide a concrete joint which is also capable of height adjustment to establish a desired reference surface height for pouring concrete.
The reference surface height (thickness) problem also applies to the construction of walls, when it is necessary to straighten the wall surface or slope when applying mortar or during plastering, to achieve a thin layer, usually less than 2-3 cm, with a high degree of precision.
Therefore, it would also be desirable to provide a surface level guide for mortar or plaster work in wall finishing.
Accordingly, it is a principal object of the present invention to overcome the disadvantages of prior art concrete expansion joints and provide a concrete expansion joint with a simple mechanism providing adjustable height, enabling faster, more efficient pouring of concrete over large layout surfaces, to achieve accurate thickness and desired slope of the concrete slab.
It is another object of the invention to provide a surface level guide for mortar or plaster work in wall finishing.
In accordance with a preferred embodiment of the present invention, there is provided an adjustable height concrete section joint assembly for placement prior to pouring a concrete slab surface, comprising:
section means extending longitudinally and being shaped for holding a flexible material; and
means for supporting said section means at an adjustable height, said height adjustment being provided before completion of pouring of concrete, such that an upper edge portion of said section means is visible at the concrete slab surface, providing it with a desired reference height and slope.
In a preferred embodiment, the concrete section joint assembly is pre-formed by use of longitudinal sections having a channel formed therein for holding elastomeric material, with the section supported from its underside by shaped support units. Each support unit is supported on a pair of threaded studs, by a specially designed nut threaded on each stud, so as to be adjustable in height. The nut has formed therein a groove into which an omega-shaped retaining spring can be inserted, to support each side of the unit. Rotation of the nut raises or lowers the height of each support unit side.
The height adjustment is provided from above the assembly and can be performed before completion of pouring the concrete, such that an upper edge portion of the elastomeric material or the upper edges of the channel are visible even with the concrete surface, providing a desired reference height and slope for the concrete surface.
This embodiment using elastomeric material provides a joint meant to eliminate the random cracks which form in the concrete.
In an alternative embodiment, the section is replaced by a rail means that extends longitudinally and is formed with a protruding inverted U-shaped middle rib with a flexible rib covering the inverted U-shaped middle rib. The rail means is supported from its underside on a pair of threaded studs, by the specially designed nut threaded on each stud, so as to be adjustable in height.
The rail means is intended to form weakness lines which guide the cracks which form in the concrete, and to provide a very accurate reference level for leveling the concrete slab surface during pouring.
The present invention is designed to allow access to the specially designed nut from above the support assembly, to allow the height and slope adjustment to be performed before and during the pouring of concrete, thus allowing greater freedom in achieving the correct adjustment, while saving set-up costs.
The inventive technique eliminates the need to saw the joint in the concrete, as with prior art methods, since the joint is ready before the concrete is poured.
In yet another alternative embodiment, the concrete expansion joint assembly section is formed from a protruding rib-like structure whose two sides are slightly open on its underside, and provided with horizontal wings extending from both sides and integral to them, the whole forming an inverted, longitudinal T-shaped profile. The assembly section is supported from its underside by a flat support unit, a suitable number of such units being appropriately spaced along the axis of the joint assembly section. The support unit is provided with pre-cut foldable tabs which, when folded over the horizontal wing surfaces of the assembly section, secure the support unit to the section. Each support unit is itself supported on a pair of threaded studs integrally formed with a raised base structure. The studs are provided with a specially-designed nut threaded on each stud, so as to be adjustable in height. The nut has formed therein a groove into which an omega-shaped retaining spring can be inserted, to support each side of the support unit. Rotation of the nut raises or lowers the height of each support unit side for leveling and aligning the joint section. As in the previously-described embodiment, the height adjustment is provided from above the assembly section and can be performed before completion of pouring the concrete, such that an upper edge portion of the section is visible even with the concrete surface to be poured, providing a desired reference height and slope for the finished concrete surface.
In another alternative embodiment, the invention provides a surface level guide for mortar or plaster work in wall finishing, comprising a rail having a protruding inverted U-shaped middle rib integrally formed with horizontal flanges, which are formed with a plurality of spaced apart mounting holes, designed to allow permanent or removable mounting of the rail.